4742 results found

#### Studying the Effect of Salt on Cress Germination

PLANNING Initial Method . Prepare 8 sterile Petri dishes with a perfectly fitting circle of cotton wool and filter paper, this will sit on top of the wool 2. A control dish must also be set up using the same steps as above 3. Weigh out 8 different salt measures, at 0.25, 0.5, 0.75, 1, 1.25, 1.5 and 1.75 4. Measure out 8, 50ml beakers of distilled water 5. Add the one measure of salt into a beaker (1 beaker for each weight) and stir until the salt is dissolved and cannot be seen 6. Add one drop of Plant nutrient growth (e.g. baby bio) to each solution 7. Add each solution into individual Petri dishes which were made up earlier on, make sure the cotton wool and filter paper are allowed a small amount of time to absorb as much water as possible before the next step 8. Add 10 Cress seeds to each of the 8 solutions and place the lid on the dish 9. Place the dishes in are area which is well lit by natural light 0. Check the dishes each day for a week and top up each dish with the same solution if it is becoming dry, add the same amount to each dish (record what you add) 1. Count and record the percentage I chose to carry out my method in this fashion as it gave me the best way to see which salt concentration had the biggest effect. I chose 8 solutions as it gives me a good range to monitor the salinity effects. The solutions are based on findings in earlier research

• Ranking:
• Word count: 1766
• Level: AS and A Level
• Subject: Science

#### Free falling experiment.

Free Falling experiment Introduction If a body is dropped from a certain height (S) falls for a time (t), then the equation of motion of a body can be written as : S= v1t+1/2gt2 Where v1 is the initial velocity. If a body is dropped from rest and falls freely then v1=0 ms-1 and the equation can be written as S=1/2gt2 Equipment Electronic timer, steel ball, contact pins, ruler and trip plate. Procedure . Set the apparatus so that the ball hits the trip plate directly. 2. The steel ball is held by electromagnet and the timer is said to read zero, as the ball released the start circuit is ON and the time of start is recorded. At the end of its fall the ball will strike the trip plate which opens the stop circuit causing the timer to stop. 3. Put the release mechanism switch ON. 4. Read out the time t for the free fall distance S. Results Distance (m) ± 0.01 st try (Sec.) ±0.005 2nd try (Sec.) ±0.005 3rd try (Sec.) ±0.005 Average Time (Sec.) ±0.005 Average Time2 (Sec.) ±0.005 .5 0.545 0.523 0.543 0.537 0.190 2 .4 0.516 0.519 0.523 0.519 0.213 3 .3 0.508 0.501 0.507 0.505 0.239 4 .2 0.487 0.487 0.492 0.489 0.255 5 .1 0.460 0.459 0.465 0.461 0.270 6 .0 0.434 0.435 0.437 0.487 0.288 Graph (Refer to the attached graphs). Conclusion Calculation of the gradient: (Y2 - Y1) / (X2 - X1)= (1.50 - 1.40) /

• Word count: 561
• Level: AS and A Level
• Subject: Science

#### The Principles and Limitations of Scanning and Transmission Electron Microscopes

The Principles and Limitations of Scanning and Transmission Electron Microscopes Electron microscopes were first developed due to the limitations of light microscopes (3). The smallest object that can be viewed by any microscope is half the wavelength of light used, and objects smaller than this cannot be seen. This is because the object has to be large enough to interfere with the waves radiation. Light has a wavelength between 400-700nm, so the smallest object that can be viewed using visible light is 200nm(3). By the early 1930's all the possible scientific progress on understanding the inner parts of cells had been made, and scientists wanted to see more detail. Max Knoll and Ernst Ruska then developed the electron microscopes in 1931 (7). Electron microscopes use the same principles as light microscopes, but a beam of electrons is used instead of a beam of light. Electron beams have a wavelength of about 0.005nm. This short wavelength means much smaller objects can be seen (3). The resolution of a microscope is its ability to distinguish between two objects that are very close together. Magnification shows the objects as one larger image. The shorter the wavelength, the better the resolution. Therefore the resolution of an electron microscope is better than a light microscope. The magnification is also better. Magnifications of x250 000 can be obtained with an electron

• Word count: 1410
• Level: AS and A Level
• Subject: Science

#### Aim To build and test a temperature sensor and analysing its suitability as a bath water thermometer.

Physics Sensing Coursework - Temperature sensor Aim To build and test a temperature sensor and analysing its suitability as a bath water thermometer. Introduction In making a temperature sensor the circuit and individual components need to be thought about. Also I need to find a way of measuring my sensor to calibrate its voltage output with the temperature it's measuring. First of all I require a component in my circuit which will change its electrical properties in the changing of temperature. This component is called a thermistor and there are two types; * The positive temperature coefficient thermistor or PTC thermistor has an increased resistance as temperature increases. These can be used as current limiters or in place of a fuse. Current through the device causes some resistive heating. If the current is too large the resistance increases due to heat increase and the current is reduced. * The negative temperature coefficient thermistor or NTC thermistor has a decreased resistance as temperature increases. Deciding on which of these to use in my circuit isn't a problem because both will change with temperature change just one has its resistance changed opposite to the other in temperature change. However there are some thermistors which are not suitable for this type of temperature measurement. Many PTC thermistors are of switching type, which means that their

• Word count: 642
• Level: AS and A Level
• Subject: Science

#### Multi-bladed Pumps. Does the number of propellor blades affect the efficiency of a water pump?

Pumps & Physics Research and Rationale What's new? When I was thinking about which aspect of physics to investigate for my investigation, I knew it was a good idea to choose something that really interested me. At the time I was becoming more and more fascinated by subatomic particles. I liked the fact that much of it was new and not understood properly, unlike the classical physics that everyone associates the subject with. Unfortunately, high energy physics does not translate into good practical coursework. However, while reading Six Easy Pieces, a book adapted from Richard Feynman's famous textbook The Feynman Lectures on Physics, I noticed that a very common everyday phenomenon is still not properly understood by physicists. Encouraged by the prospect of discovering something new, I read on. Chaotic ideas Feynman wrote (on page 66) "There is a physical problem that is common to many fields, that is very old, and that has not been solved...It is the analysis of circulating or turbulent fluids...No-one can analyse it from first principles" "Wow - something science can't explain" I thought. I looked on the internet for further details and I found a poster from World Maths Year 2000 (http://www.newton.cam.ac.uk/wmy2kposters/march/), showing just the type of unpredictable fluid motion that Feynman was writing about. It's a new and exciting branch of maths called

• Word count: 7663
• Level: AS and A Level
• Subject: Science

#### To find out how different masses affect the period of one oscillation of a spring.

PHYSICS COURSEWORK AIM: To find out how different masses affect the period of one oscillation of a spring. PLANNING: INTRODUCTION: A spring is elastic, therefore has elastic properties and this is why it oscillates. The spring can harness elastic energy in its coils as it is pulled down. When masses are hung from the spring, it gains gravitational potential energy that causes a resultant force and the spring as a result is pulled down. It also gains some kinetic energy along with the elastic energy. Then, the forces balance out and there is no movement. At this point energy is converted to elastic and the spring pulls back up again. As it goes up, the shape restores and gains gravitational potential energy again. At the top, the forces balance, then is converted back into gravitational potential energy, and again, a resultant force is created that pulls the spring down. In this experiment, what I am planning to do is to find out how different masses affect the period of one oscillation of a spring. This is done by setting up a stand and a clamp. Hanging off the clamp will be the spring. Then a weight carrier will be hung off the spring, and this is where the different masses will be placed. The spring has a restrain force but this shouldn't affect the experiment because it will be extended by the weight carrier. Diagram: The masses will make the spring oscillate and

• Word count: 963
• Level: AS and A Level
• Subject: Science

#### The Chemistry oh Phosphorous

The Chemistry of Phosphorus Among the non-metals, on the right hand side of the periodic table, with Atomic Number 15, is the element Phosphorus. The word 'phosphorus' is derived from the Greek word 'phosphoros' meaning 'bringer of light' and its discovery was completely accidental. It has the electronic configuration 2,8,5 and has 5 electrons in its outer most shell, hence it being in group 5 of the periodic table, under Nitrogen. In 1669, German alchemist Hennig Brand was attempting to create the 'philosopher's stone', which was a supposedly magical substance that would turn metals into gold, by evaporating urine. One day, after boiling urine into a paste, heating the paste to a high temperature and passing the vapours through water, where he hoped to find gold, was a mysterious white waxy substance that seemed to glow in the dark, and burst into flames when in contact with air. Brand had discovered phosphorus, well was the first to record this discovery. In fact, several other chemists could have discovered it at a similar time, and we now know that the substance he found was actually ammonium sodium hydrogen phosphate: (NH4)NaHPO41. This method produced only about 60g of phosphorus and used 1100L of urine, so was not very efficient, and it was only later on that investigators found alternative methods of obtaining it. One of its current processes of production

• Word count: 2294
• Level: AS and A Level
• Subject: Science

#### Demonstrate an understanding of the theory, principles and practice of separation of liquid mixtures by distillation techniques

• Word count: 1440
• Level: AS and A Level
• Subject: Science

#### An Investigation into Hooke's Law - The aim of this experiment is to find out if the amount of weight applied to an elastic or stretchable object is proportional to the amount the object's length increases by when the weight is applied.

An Investigation into Hooke's Law Planning The aim of this experiment is to find out if the amount of weight applied to an elastic or stretchable object is proportional to the amount the object's length increases by when the weight is applied. Since Hooke's law is famous, and is used a lot, I have many resources and researchable information available to use. I took this from a website; http://www.efunda.com/formulae/solid_mechanics/mat_mechanics/hooke.cfm "Robert Hooke, who in 1676 stated, The power (Sic.) of any springy body is in the same proportion with the extension. He announced the birth of elasticity. Hooke's statement expressed mathematically is, where F is the applied force (and not the power, as Hooke mistakenly suggested), u is the deformation of the elastic body subjected to the force F, and k is the spring constant (i.e. the ratio of previous two parameters)." The equation will be very useful in calculating the change in size, and for preparing my hypothesis. I took this from http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0021767.html. Elasticity (physics) In physics, the ability of a solid to recover its shape once deforming forces (stresses modifying its dimensions or shape) are removed. An elastic material obeys Hooke's law, which states that its deformation is proportional to the applied stress up to a certain point, called the

• Word count: 1675
• Level: AS and A Level
• Subject: Science

#### Green Chemistry - greenhouse gases and the ozone layer

The 'Greenhouse effect' ? The greenhouse effect keeps us warm ? But, the enhanced greenhouse effect is responsible for global warming. Infrared radiation comes into the atmosphere and gets absorbed by the C=O, O-H and C-H bonds in H2O, CH4 and CO2. They vibrate gaining EK, which is dispersed, warming the Earth's surface. The greenhouse effect of a given gas is dependent on the: ? Concentration in the atmosphere (High CO2 etc) ? The ability to absorb infrared radiation (i.e. the bonding in it) The IPCC (bunch of chemists) collects evidence to force governments to stop producing so much CO2. Scientists should research ways in which global warming can be reduced ? Carbon-Capture and Storage (CCS)- This involves converting CO2 into liquid form. This liquid can be injected deep underground. ? Also reaction with metal oxides to form carbonates. (Magnesium Oxide) MO(s) + CO2(g) --> MCO3(s) ? The Kyoto Protocol was signed by developed nations governments to reduce output of greenhouse gasses to offset the progress of global warming. The scheme involved using carbon credits which can be traded around to penalise polluting nations. Some nations (Australia, USA (Obama)) are reluctant to join because of the impact on their economies.(See Geog notes) The ozone layer The Ozone Layer absorbs much of the harmful ultraviolet radiation emitted by

• Ranking:
• Word count: 928
• Level: AS and A Level
• Subject: Science